Add the stringify method

[sergkudinov]

Add the stringify method, documentation and tests.

The method converts an array, which is result of the compile method, to a CLI command string. For example:
If the Parameters config is:

{
  commands: { 
    'start': {
      options: {
        'myparam': {}
}  }  }  }

The script like this:

parameters(config).stringify({
  command: 'start',
  myparam: 'my value'  
})

will output this:

process.execPath ./bin/myscript start --myparam ‘my value'

[wdavidw]

I dont understand, is it exactly what stringify (soon to be called compile) method is doing ? Stringify, in its new version shall return a string, not an array.

[sergkudinov]

Forgot to change copy paste. Changed